I found one site that claimed the orifice was installed only on a bout six planes during the Battle of Britain, and was never in wide usage. go here for that article: http://www.inventricity.com/tilly-shilling
This is not in accord with the other sources I've found, all of which are clear that Tilly and her team helped squadrons install RAE restrictor as she went from base to base, starting with the front line stations. By 1941, it is generally argued, the device was almost universally installed. So we should probably see it in WB planes no later than with the introduction of the SpitVB. It it may have been in service before then, but that would be a good compromise date.
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"The Tilly orifice
Complaints from pilots led to a concentrated search for a solution. Engine manufacturers Rolls-Royce produced an improved carburettor, but this failed in testing. It was Beatrice 'Tilly' Shilling, an engineer working at the Royal Aircraft Establishment at Farnborough, who came up with a simple device which could be fitted without taking the aircraft out of service. She designed a thimble-shaped brass flow restrictor (later refined to a flat washer) with precisely calculated dimensions to allow just enough fuel flow for maximum engine power. It came in two versions, one for 12 psi manifold pressure and another for the 15 psi achieved by supercharged units.[3]
While not completely solving the problem, the restrictor, along with modifications to the needle valve, permitted pilots to perform quick negative G manoeuvres without loss of engine power. This improvement removed the RAF's Rolls-Royce Merlin-powered fighters' drawback versus the German Messerschmitt Bf 109E machine, whose Daimler-Benz DB 601 inverted V12 powerplant had had fuel injection since 1937. During early 1941, Miss Shilling travelled with a small team to fit the restrictors in one RAF base after another, giving priority to front-line units. By March 1941 the device had been installed throughout RAF Fighter Command. Officially named the 'R.A.E. restrictor', the device was immensely popular with pilots, who affectionately named it 'Miss Shilling's orifice' or simply the 'Tilly orifice'.
This simple measure was only a stopgap: it did not allow inverted flight for any length of time. The problems were not finally overcome until the introduction of Bendix and later Rolls-Royce pressure carburetors in 1943. "
Start watching at 50 seconds into video that shows no orfice, then continues with the how and why's and the help, but not complete fix of the RAE restrictor.
It absolutely wasn't a complete fix. But... it did allow several seconds of negative G, which was enough to bunt over to follow an enemy. I think we need to add those few seconds to the planes that should have them. Spit II and beyond probably. Even with it... Inverted flight for any length of time would be um... problematic.
Unfortunately the engine cutout can not be set with a timer, the code only allows for a negative G-limit. As such the Spit I, II & Vb have been set to cutout at even small neg G forces, while the Spit Vc & IXa will require a larger neg G force to cutout. It's the best we can do with the code to simulate the Miss Shilling's Orifice.
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